Buyers of industrial control panels often conflate two different suppliers. A UL 508A panel shop designs and builds the populated control panel and applies the UL 508A listing to the assembly. A contract enclosure fabricator builds the enclosure — the sheet-metal or stainless box, with its own UL 50/50E listing where required — and sells it to the panel shop, the OEM or the plant. Understanding the division makes both purchases go better. This post explains who does what.
Panel shop or OEM looking for a custom enclosure source? Call 601.892.5017 or email collin.t@fabtekindustries.com — send a print and a quantity and we’ll quote it.
- UL 508A covers the industrial control panel as an assembly; UL 50/50E covers the enclosure as a product. Different suppliers hold each.
- A panel shop buys the enclosure from a catalog or from a custom fabricator, then populates, wires and lists the panel.
- Panel shops go custom when the size, material, cutouts or rating are not in the catalog, or when volume justifies a kit.
- OEMs and plants can buy the enclosure direct and the panel work separately, or buy a finished panel from a shop that sources the enclosure — but the drawing has to say which.
What a UL 508A panel shop does
UL 508A is the standard for industrial control panels — the populated assembly of enclosure, disconnect, overcurrent protection, contactors, drives, PLCs, terminal blocks and wiring that controls a machine or process. A UL 508A panel shop has a UL program that lets it design the panel to the standard, select listed components, calculate the short-circuit current rating, build and wire it, and apply the UL 508A label. That label is what the authority having jurisdiction and the end customer look for. The panel shop owns the design, the component selection, the SCCR and the listing. What it usually does not own is a laser, a press brake and a powder line.
What an enclosure fabricator does
A contract enclosure fabricator builds the box: cut, formed, welded, hardware-installed and finished sheet metal, stainless or aluminum, to a drawing. Where the specification requires it, the enclosure carries a UL 50/50E listing — the standard for enclosures for electrical equipment, which covers the enclosure’s construction and its environmental type rating (NEMA 1, 12, 3R, 4, 4X and so on). FabTek holds UL 50/50E listing on its enclosures and builds control cabinets, NEMA 4X enclosures and switchgear housings to print; what the listing covers is explained in UL 50/50E listed enclosures explained. The fabricator does not select components, calculate SCCR or list the panel.
| UL 508A | Industrial control panel assembly · held by the panel shop · covers design, components, SCCR, wiring, marking |
|---|---|
| UL 50 / 50E | Enclosure for electrical equipment · held by the enclosure manufacturer · covers construction and environmental type rating |
| Where they meet | A 508A panel built in a listed 50/50E enclosure of the right type satisfies both the panel and the environmental requirement; a 508A panel in an unlisted custom enclosure requires the panel shop to evaluate the enclosure under its program |
When a panel shop goes custom
- Size — the panel does not fit a catalog enclosure, or a catalog enclosure wastes space the machine does not have.
- Material and rating — 316 stainless 4X with a sloped top, aluminum for weight, or a specific gauge the end customer requires.
- Cutouts and mounting — HMI, disconnect, cooler and pushbutton cutouts pre-cut so the shop does not spend hours on a hole saw; machine-specific mounting feet.
- Volume — an OEM machine builder shipping the same panel every week benefits from a kitted custom enclosure at a lower cost than catalog plus modification.
- Appearance — the OEM’s color, logo embossing or a console shape the catalog does not offer; see operator consoles and HMI pedestals.
How OEMs and plants buy from both
Two structures work. In the first, the OEM or plant buys a finished, listed panel from the 508A shop, and the shop buys the enclosure from the fabricator; the fabricator’s customer is the panel shop, and the enclosure drawing comes from the shop. In the second, the OEM buys the enclosure directly from the fabricator — often because it controls the design or wants the volume pricing — and furnishes it to the panel shop for population; here the OEM owns the enclosure drawing and the panel shop confirms it meets the type rating the panel needs. Both work when the drawing states the enclosure type, the listing requirement and who holds it. The industrial control panel enclosure guide covers the enclosure spec in detail.
The panel shop–fabricator relationship
The best version of this relationship looks like an OEM program: the panel shop standardizes a few enclosure families for its repeat customers, the fabricator holds the drawings and stages material, and enclosures arrive kitted with cutouts and hardware so the shop’s labor goes into wiring, not metalwork. A panel shop that is turning away work for lack of enclosure capacity, or spending its technicians’ hours modifying catalog boxes, usually has a custom program waiting to be set up. What a fabricator needs to quote is where that starts.
The panel shop’s value is the wiring, the SCCR and the label. Every hour it spends on a hole saw is an hour it is not doing that.
FabTek Industries fabricates custom enclosures for UL 508A panel shops, machine builders and plants — control cabinets, stainless NEMA 4X enclosures, consoles and junction boxes, with cutouts and hardware to print, UL 50/50E listed where required, powder-coated in-house — under an ISO 9001:2015 quality system, from four production sites in Hazlehurst, Mississippi. See how we work with electrical OEMs, or send us a print.
Working on something like this? Send a print or a scope — pricing and lead time within one business day, from four Mississippi plants.
Frequently asked questions
What is the difference between UL 508A and UL 50/50E?
UL 508A is the standard for industrial control panels as populated assemblies — design, listed components, short-circuit current rating, wiring and marking — and is held by the panel shop. UL 50 and 50E are the standards for enclosures for electrical equipment — construction and environmental type rating — and are held by the enclosure manufacturer.
Does a contract enclosure fabricator list the control panel?
No. The fabricator builds the enclosure and may hold a UL 50/50E listing on it. The UL 508A panel shop designs, populates, wires and lists the panel assembly.
Why would a panel shop buy a custom enclosure instead of a catalog one?
When the size, material, type rating, cutouts or mounting are not available in the catalog, when the appearance or shape matters, or when repeat volume makes a kitted custom enclosure cheaper than a catalog enclosure plus modification.
Can an OEM buy the enclosure directly and have a panel shop populate it?
Yes. The OEM owns the enclosure drawing and furnishes the enclosure; the panel shop confirms it meets the type rating the panel requires and builds and lists the panel in it. The drawing should state the enclosure type, the listing requirement and who holds it.
